I'm baffled. How a phone that is both a writing utensil and a device for making calls to other humans—humans who might also be writing with their pen phones when I call upon them—could fail is beyond me. More »
Consumer Electronics - Shopping - Arts - Association football - Science and Technology
i have a 1995 chevy s-10 with a 4.3 engine in it and an automatic transmission, its the transmission that the gears shift electronically i put a transmission in it but low gear does not work the transmission was taken out of a chevy blazer that was used every day until it was wrecked, low gear worke
In humans, two chromosomes – X and Y – determine whether we are male or female. Of the two, Y tends to get more attention because of its small, degenerate size. Both X and Y probably evolved from a pair of ordinary chromosomes that have nothing to do with sex (also known as autosomes). The story goes that one of these autosomes developed a gene that immediately caused its bearer to become male, and eventually became the Y chromosome of today. The other one became X.
Throughout its history, Y has been a hotbed of genetic change, gaining, losing and remodelling its genes at breakneck pace, and shrinking by 97%. Its partner – X – has allegedly had a less eventful past, and should faithfully represent the ancestral autosome. This history of X and Y was first proposed in 1914 by Herman Muller, and ever since, his assumptions about X’s stability have gone untested. Now, it seems that Muller was wrong. Daniel Bellott from the Howard Hughes Medical Institute had uncovered the secret history of X, which turns out to be no less storied than Y’s tale.
Bellott’s work began, surprisingly, with chickens. Birds also have sex-setting chromosomes, known as Z and W, which vary between the males and females. The big difference is that in birds, males are ZZ and females are ZW – obviously in humans, males are the ones with the differing pair. Like the Y chromosome, W has shrunk and changed considerably while, as Bellott says, “the sex chromosomes that are present in both sexes (X and Z) were supposed to be above the fray”.
But Bellott showed that this isn’t true by completely sequencing the Z chromosome for the first time. (The chicken genome has been published before but sex chromosomes are notoriously difficult to sequence). His draft revealed that both X and Z arose from different autosome ancestors, and none of the 1,000 genes on the Z chromosome has a counterpart on the X. Nonetheless, they have independently evolved very similar features.
Both are very loosely packed with genes. In any given stretch of DNA, the Z and X chromosomes have half as many genes as other autosomes do. And among these patchily distributed genes are piles of litter – long stretches of repetitive DNA with no clear function. Most of these are sequences known as LINEs. “These LINEs are basically selfish elements,” says Bellott. “If a cell is like a computer, the genome is like a hard drive, and the LINEs are computer viruses that copy themselves over and over, filling up the drive.” Z has 70% more LINEs than any other chicken autosome.
The LINEs can’t quite account for all the extra space between the genes, but that might just be because they’ve decayed over time. Bellott explains, “We think that, for whatever reason, the mechanisms for cleaning out this “junk DNA” are less effective on Z and X chromosomes than on autosomes. As a result, junk builds up in between the genes on the Z and X, but because it doesn’t really do anything for the organism, it slowly decays. After a while, we can’t even recognize the “junk” as LINEs anymore. After millions of years as sex chromosomes, it just looks like the X and the Z have a low gene density.”
Why the similarities? It’s possible that both X and Z evolved from autosomes with features that made them more likely to become sex chromosomes. Perhaps, for example, their genes were already sparsely distributed. But Bellott ruled out this idea. He compared X to its closest counterpart in chicken, and Z to its equivalents in humans – none of these relatives had any structural features that made them stand out among other autosomes. There’s nothing that singles them out as ideal candidates for the role of sex chromosome.
So it seems that X and Z chromosomes are true examples of convergent evolution – when two entities take different evolutionary roads to arrive at the same adaptive destinations. Not only have their genes become more widely spread apart, they have also gained extra ones. While the tiny Y and W chromosomes have jettisoned genes at great speed, X and Z seem to have gained genes since their ancient days as autosomes.
The identity of these added genes is particularly surprising – they’re mostly male-specific genes that are only switched on in the testes. And there are lots of them, arrayed in a huge block. These testes-genes make up around a sixty of the Z chromosome and 1% of the chicken’s entire genome!
This is particularly surprising because the Z chromosome is present twice in male birds, but the X chromosome is only present once in male humans. You might have expected, for example, the X chromosome to be richer in female-specific genes. Bellott says, “The convergent specialization for testis function suggests that there are strong evolutionary pressures on male reproduction.” Indeed, other studies have suggested that traits related to male reproduction are some of the fastest evolving characteristics in the animal kingdom. These pressures are strong enough to trump any difference in the XY and ZW sex-setting systems.
Reference: Nature http://dx.doi.org/10.1038/nature09172
More on sex chromosomes:
If the citation link isn’t working, read why here
Blockbuster? We knew it was dying, courtesy Redbox, Netflix and the changing ways people consume their entertainment, but when will it finally expire? Probably next year, according to one analyst and the company's own balance sheet. Updated. More »
Blockbuster - Netflix - Business - redbox - Rental shop
Hello;
I have a question about castings. I need to determine exactly what type of casting I have.
I need to repair four holes that are stripped of the threads and also have two broken studs in them. The holes are about one inch dia.
The casting is part of a backhoe. It is the main pivot that
I wanted to use my DELL 2006 LCD monitor as a TV set. After various exchanges with people I was told to buy the above cable and connect it to my SONY RDR-HX780 Tivo using the component video output RCA sockets labelled Y, PB, PR. I bought the cable and plugged it in but nothing happens at all. Am I
It could be the dams, fertilizers, pesticides, and related reduced food availability. It might have to do with the amount of water in the region, climate change, and poor regulation. Most likely, it's some combination of these factors compounded by widespread apathy about a population of chinook salmon off the coasts of Northern California--until it was too late. The Press Democrat quoted fisherman Al Vail: “I never caught a fish,” he said. “I've never seen a year like this, and I've been fishing for 45 years.” Sad, but is anyone surprised? Those with an eye to the fishery knew this news would come. The farmers, the environmentalists, the scientists, the fishermen, and much of the public observed and waited. Tragedy of the commons? Perhaps. Tragedy for the fishery and those involved in industry? Obviously. Next up... Blue Fin Tuna?
I'm reminded of Kurt on the fate of the planet in Man Without A Country: "We could have saved it, but we were too damn cheap and lazy."
Were you a Comcast subscriber between April 1, 2006 and December 31, 2008? Did you use Ares, BitTorrent, eDonkey, FastTrack, or Gnutella? Yes? Then it's payday for you, to the tune of $16, as the now infamous PSP class action lawsuit against Comcast has resulted in a previous mentioned $16 million settlement fund. You have until August 29, 2010 to file a claim. [Ars Technica] More »
Class action - Comcast - File sharing - BitTorrent - Clients
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In generator winding the conductors has much needed forced cooling by Water and/or Hydrogen. The current flow in Generator bus bar in bus duct is also same as in Generator winding but the not that much of cooling is required. In case of 500 MW / 0.8 pf generator the full load cu
The operating temperature of copper in cables with different insulations(pvc,xlpe,rubber etc) differs from each other. When a cable is connected to a switchgear(mcb,mccb,acb etc)is there any derating factor given by swgr manufacturers to be applied when selecting swgr?.
(HealthDay News) -- Eating a Mediterranean diet may help keep your brain healthy as you age, findings from an ongoing study show.
"This diet emphasizes vegetables, fruits, fish, olive oil, lower meat consumption, and moderate wine and non-refined grain intake," study author Dr. Christy Tangney, of Rush University Medical Center in Chicago, said in a news release from the American Society for Nutrition.
Rather than asking people to avoid certain foods, the study found data that "adults over age 65 should look to include more olive oil, legumes, nuts, and seeds in their diet in order to improve their recall times and other cognitive skills, such as identifying symbols and numbers," Tangney said.
The study included 4,000 adults aged 65 and older who were given a series of tests to examine their cognitive (or thinking) skills every three years over a 15-year period. Those who scored highest in following a Mediterranean diet were least likely to suffer cognitive decline, the study authors found. Read more...
I haven't been to Burger King in a long while, but if the States implemented the "musical shower" heads that the Japanese experience in their "upscale" Burger Kings, I could be enticed back into the glutinous fold one last time. More »
Fast Food - BurgerKing - Recreation - Food - Business
Can two alternators of unequal capacity be run in parallel ?
Click here to view the embedded video.
Another milestone in the Shuttle program is reached.
Given the current events and attitudes I wonder how long it will be before NASA gets a name change to perhaps: National Aeronautics and Science Administration. Hey don’t laugh, it could happen, I wouldn’t be surprised in the least.
Fujitsu, former iPad trademark owner and soft-spoken tech manufacturer, is jumping into the Android smartphone game. It will be the company's first smartphone since it stopped selling the multifaceted devices back in 2007. More »
Fujitsu - Android - Smartphone - Handhelds - Toshiba
Please add an option on the edit member profile page
to disable the CR4 spell checker
which requires far too many mouse clicks
both of the supported browsers support right click spell checking
but the CR4 editor gets in the way & adds once again too many mouse clicks to the process
The solar tracker/concentrator is coming along, now I'm up to the point of integrating the trough collector and the heat tank.
Basically I've got a copper tube running the focus of my parabolic trough, and to each end of this I want to attach a hose, they in turn connected to a tank for sto
Sir, I wish to pursue under graduate course in bio medical engineering and would like to know the field of study is all about and how does it compare with Electronics and Communication Engineering. what are all the opportunities for pursuing post graduation in India and job opportunities in India. (
One mysteriously labeled AT&T "VIP" customer (they've complained, politely? Love wearing AT&T t-shirts?) has been gifted one of those handy MicroCell, and no one seems to know why. Viral marketing stunt? Rounding error? Whatever. Free 3G femtocell: Updated. More »
iPhone - Smartphone - Handhelds - 3gMicrocell - Apple
If it has been previously discussed, I apoligize...If not...Here we go.
I currently use a cleaning / passivation procedure for field built SS tanks utilizing Ecolab products. Rinse, Sterbec (Quaternary Ammonia), rinse, degrease with Accomplish (Sodium Hydroxide & surfactant additives) rins
